EPERLECQUES SE Wastewater Treatment Plant, Éperlecques, Hauts-de-France

EPERLECQUES SE is a wastewater treatment facility located in Éperlecques, a commune in the Pas-de-Calais department of Hauts-de-France, northern France. The plant serves a population of 1,658 and is part of the region's municipal wastewater infrastructure, operating under French regulations that transpose the EU Urban Waste Water Treatment Directive (91/271/EEC). The plant employs advanced treatment processes, which go beyond the secondary treatment standard required by the EU directive for agglomerations of this size. With a designed capacity of 3,960 m³/day and a current discharge volume of 295.78 m³/day, the facility operates well below its capacity, indicating room for future growth or seasonal variability. The treated effluent is discharged into local watercourses that ultimately drain into the North Sea via the Aa River basin. The plant plays a key role in protecting the region's waterways from nutrient pollution and organic load, supporting aquatic life and downstream ecosystems in the Flanders coastal plain.

The plant discharges into the Aa River basin, which flows through the low-lying plains of Hauts-de-France before reaching the North Sea near Gravelines. This watershed supports diverse aquatic habitats and is important for migratory fish species. The advanced treatment helps reduce nutrient loads that could otherwise contribute to eutrophication in the coastal zone, an area sensitive to algal blooms and oxygen depletion.